As you may know, the MATE desktop environment is a Gnome2 fork, created a few months after the Ubuntu systems switched to Gnome3.
Because some popular Linux operating systems like Debian, OpenSUSE and Fedora decided to create their systems running on Wayland as a display server in the future, the MATE developers decided to add support for the Wayland Weston display server and systemd.
This information was discusses at the openSUSE conference in Greece. For more information about MATE getting Wayland support, see this video from the conference.
For those who don’t know yet, Wayland is a simple replacement for the X.org display server.